News & Views Nutrition & Feed products Research
Video, tagging methods can optimize pellet intake in Rainbow trout: study

Scientists in Germany have developed a novel methodology and parameter for minimum pellet intake (MPI) for juvenile Rainbow trout that could lead to cost-efficiency and better water quality.

Accuracy in pinning down MPI will enable farmers to maximize pellet uptake and minimize feed waste. The German scientists said this could be done using video surveillance.

Philip Just and his team conducted an experiment to analyze individual diet uptake in juvenile rainbow trout. During the study, all subjects were code-tagged, and high-quality video images were taken and analyzed to identify all feeding interactions.

Just is a scientist working on his PhD at the Alfred-Wegener-Institute Helmholtz-Centre for Marine and Polar Research in Bremerhaven, Germany, where the experiments were conducted.

“By the use of the video evaluation method in this study, it was possible to maximize the minimum pellet intake (MPI),” told Hatchery International. “Further, the homogeneity of pellet intake was increased by feeding unstarved rainbow trout twice daily with multiple portions.”

With the applied feeding regime, the chance that each individual ingests a nominal minimum of 20 pellets (≈1 per cent body weight of fish−1) is maximized to nearly 100 per cent, the team cited in the study, “Video surveillance methods to evaluate individual feeding response in rainbow trout (Oncorhynchus mykiss, Walbaum) — implications for feeding regime optimization,” published in Aquaculture International.

Three trials tested the impact of short-term starvation, portion number per feeding and varied numbers of daily feeding events. These were conducted in recirculating system with tanks with clear-glass fronts.

“The video method applied with extremely low-impact individual tagging of fish proved highly effective, although it is a time intensive tool to determine individual food uptake. It allowed the development of direct measures for evenness of diet uptake across a group of individual fish and provides insights into the efficacy of various known feeding regimes/methods considered viable for improving diet uptake,” they said.

The MPI parameter they developed can also play a role the application of oral veterinary treatment or vaccines. “This means a guarantee for an uptake of x units vaccine,” Just said.